An evaluation of Home Office extended interviews for police personnel

Abstract

In this thesis the validity of an Assessment Centre (called 'Extended Interview') operated on behalf of the British police is investigated. This Assessment Centre (AC) is used to select from amongst internal candidates (serving policemen and policewomen) and external candidates (graduates) for places on an accelerated promotion scheme. The literature is reviewed with respect to history, content, structure, reliability, validity, efficiency and usefulness of ACs, and to contextual issues surrounding AC use. The history of, background to and content of police Extended Interviews (Els) is described, and research issues are identified. Internal validation involved regression of overall EI grades on measures from component tests, exercises, interviews and peer nominations. Four samples numbering 126, 73, 86 and 109 were used in this part of the research. External validation involved regression of three types of criteria - training grades, rank attained, and supervisory ratings - on all EI measures. Follow-up periods for job criteria ranged from 7 to 19 years. Three samples, numbering 223, 157 and 86, were used in this part of the research. In subsidiary investigations, supervisory ratings were factor analysed and criteria intercorrelated. For two of the samples involved in the external validition, clinical/judgemental prediction was compared with mechanical (unit-weighted composite) prediction. Main conclusions are that: (1) EI selection decisions were valid, but only for a job performance criterion; relatively low validity overall was interpreted principally in terms of the questionable job relatedness of the EI procedure; (2) Els as a whole had more validity than was reflected in final EI decisions; (3) assessors' use of information was not optimum, tending to over-emphasize subjectively derived information particularly from interviews; and (4) mechanical prediction was superior to clinical/judgemental prediction for five major criteria.